He is a great coach and will do a great job for you guys. I am a little perturbed that he had no loyalty to his current players, and I don't think this is a matter of money but probably more a matter of control.
As others have mentioned, there seems to be an issue between Knowles and LJ. Day called LJ the greatest line coach in college history at the national championships celebration today. This year Ohio state's defense improved tremendously after the first Oregon game and in particular the linebackers were much improved which I attribute to James laurinaitis. The change in the defensive coordinator will probably hamper recruiting a little bit but if there was friction it is just as good to get it behind everybody. When Ryan day goes outside of Ohio State legacy coaches, he has a good record of choosing assistant coaches. For instance, Jeff Hafley was a really good defensive coordinator when Day first became head coach.